Microfibrillated cellulose fibers consist of a part or the whole of the fibers having extremely fine fibers, of specifically tens of cellulose chains thereof having the fineness of microfibrill level. So far, various methods for manufacturing microfibrillated cellulose fibers have been proposed. For example, a method of obtaining bacteria cellulose by fermentation using of acetobacter, a method for making pulp into microfibrillated fibers also using an abrasive grinding apparatus (JP 7-310296 A), and a method for treating pulp for a long period of time using a high pressure homogenizer have been proposed.
Any of such methods, however, requires a specially designed equipment and high energy, and the properties of the resulting final products are not consistent. At present, no method of continuously manufacturing microfibrillated cellulose fibers for an industry has been realized yet.
Note that in the paper manufacturing field, as a high efficiency beating and fibrillating machine, disc refiners such as a single disc refiner and a double disc refiner (hereinafter “DDR”) are widely and generally used. Attempts have been made to obtain more finely microfibrillated cellulose fibers using the disc refiners. An example is a process of making highly beaten and fibrillated pulp which is used as a raw material for parchment paper.
In the above-mentioned process, however, it has been said that it is difficult to reach the micro refined level of microfibrillated cellulose fibers. Besides, no reports have been made that MFC has been obtained by means of a disc refiner.